Observation of a new Xib- resonance - arXiv

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May 23, 2018 - [33] D. J. Lange, The EvtGen particle decay simulation package, Nucl. ..... Altas Enerxıas (IGFAE), Universidade de Santiago de Compostela,.
EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH (CERN)

arXiv:1805.09418v1 [hep-ex] 23 May 2018

CERN-EP-2018-108 LHCb-PAPER-2018-013 May 23, 2018

Observation of a new Ξb− resonance

LHCb collaboration†

Abstract √ From samples of pp collision data collected by the LHCb experiment at s = 7, 8 and 13 TeV, corresponding to integrated luminosities of 1.0, 2.0 and 1.5 fb−1 , respectively, a peak in both the Λ0b K − and Ξb0 π − invariant mass spectra is observed. In the quark model, radially and orbitally excited Ξb− resonances with quark content bds are expected. Referring to this peak as Ξb (6227)− , the mass difference and natural width are measured to be mΞb (6227)− = 6226.9 ± 2.0 ± 0.3 ± 0.2 MeV/c2 and ΓΞb (6227)− = 18.1 ± 5.4 ± 1.8 MeV/c2 , where the first uncertainty is statistical, the second is systematic, and the third, on mΞb (6227)− , is due to the knowledge of the Λ0b baryon mass. Relative production rates of the Ξb (6227)− → Λ0b K − and Ξb (6227)− → Ξb0 π − decays are also reported.

Submitted to Phys. Rev. Lett. c 2018 CERN for the benefit of the LHCb collaboration, licence CC-BY-4.0.



Authors are listed at the end of this paper.

ii

In the constituent quark model [1, 2], baryonic states form multiplets according to the symmetry of their flavor, spin, and spatial wave functions. The masses, widths and decay modes of these states give insight into their internal structure [3]. The Ξb0 and Ξb− states form an isodoublet of bsq bound states, where q is a u or d quark, respectively. Three such isodoublets, which are neither radially nor orbitally excited, should exist [4], and include one with spin jqs = 0 and J P = (1/2)+ (Ξb ), a second with jqs = 1 and J P = (1/2)+ (Ξb 0 ), and a third with jqs = 1 and J P = (3/2)+ (Ξb ∗ ). Here, jqs is the spin of the light diquark system qs, and J P represents the spin and parity of the state. Three of the four jqs = 1 states have been recently observed through their decays to Ξb0 π − and Ξb− π + [5–7]. Beyond these lowest-lying states, a spectrum of heavier states is expected [8–23], where there are either radial or orbital excitations amongst the constituent quarks. The only such states discovered thus far in the b-baryon sector are the Λb (5912)0 and Λb (5920)0 resonances [24], which are consistent with being orbital excitations of the Λ0b baryon. In this Letter, we report the first observation of a new state, decaying into both Λ0b K − and Ξb0 π − , using samples of pp collision data collected with the LHCb experiment at 7, 8 and 13 TeV, corresponding to integrated luminosities of 1.0, 2.0 and 1.5 fb−1 , respectively. The observation of these decays is consistent with the strong decay of a radially or orbitally excited Ξb− baryon, hereafter referred to as Ξb (6227)− . Charge-conjugate processes are implicitly included throughout this Letter. The mass and width of the Ξb (6227)− baryon are measured using the Λ0b K − mode, where the Λ0b baryon is detected through its fully reconstructed hadronic (HAD) decay to − 0 0 Λ+ c π . Larger samples of semileptonic (SL) Λb and Ξb decays are used to measure the production ratios fΞb (6227)− B(Ξb (6227)− → Λ0b K − ), fΛ0b fΞ (6227)− R(Ξb0 π − ) ≡ b B(Ξb (6227)− → Ξb0 π − ), fΞb0

R(Λ0b K − ) ≡

(1) (2)

where fΞb (6227)− , fΞb0 and fΛ0b are the fragmentation fractions of a b quark into each baryon and B represents a branching fraction. Here, the Λ0b and Ξb0 baryons are detected − 0 + − using Λ0b → Λ+ c µ X and Ξb → Ξc µ X decays, where X represents undetected particles. 0 + + Throughout the text, Hb (Hc ) is used to designate either a Λ0b or Ξb0 (Λ+ c or Ξc ) baryon. Owing to much larger branching fractions, the SL signal yields are about an order of magnitude larger than that of any fully hadronic final state, which enables the observation of the Ξb (6227)− → Ξb0 π − mode. The SL decays are not used in the Ξb (6227)− mass or width determination, as they have larger systematic uncertainties due to modeling of the mass resolution. The LHCb detector [25, 26] is a single-arm forward spectrometer covering the pseudorapidity range 2 < η < 5, designed for the study of particles containing b or c quarks [25, 26]. The tracking system provides a measurement of the momentum, p, of charged particles with a relative uncertainty that varies from 0.5% at low momentum to 1.0% at 200 GeV/c. The minimum distance of a track to a primary vertex (PV), the impact parameter (IP), is measured with a resolution of (15 + 29/pT ) µm, where pT is the component of the momentum transverse to the beam, in GeV/c. Different types of charged hadrons are distinguished using information from two ring-imaging Cherenkov detectors [27]. The online event selection is performed by a trigger, which consists of a 1

hardware stage, based on information from the calorimeter and muon systems, followed by a software stage, which applies a full event reconstruction [28, 29]. Simulated data samples are produced using the software packages described in Refs. [30–36]. − + − + − Samples of Λ0b (Ξb0 ) are formed from Λ+ c π and Λc µ (Ξc µ ) combinations, where + − + + Λ+ c and Ξc decays are reconstructed in the pK π final state. The Hc decay products must have particle identification (PID) information consistent with the given particle hypothesis, and be inconsistent with originating from a PV by requiring each to have large χ2IP with respect to all PVs in the event. Here χ2IP is the difference in χ2 of the vertex fit of a given PV when the particle (here p, K − or π + ) is included or excluded from the fit. The Hc+ candidate is required to have a fitted vertex significantly displaced from all PVs in the event and have an invariant mass within 60 MeV/c2 of the known Hc+ mass. The Hc+ background is dominated by random combinations of tracks from nonsignal b-hadron decays. In the Ξc+ sample, about 15% of this background is due to misidentified D+ → K − π + π + , D+ → K + K − π + , Ds+ → K + K − π + and D∗+ → (D0 → K − π + )π + decays. These cross-feed contributions are suppressed by employing tighter PID requirements on candidates that are consistent with being one of these charm mesons, with only a 1% loss of signal efficiency. These tighter requirements are not applied to the Λ+ c sample, as the cross-feed contributions are negligible. Muon (pion) candidates with pT > 1 GeV/c (0.5 GeV/c) and large χ2IP are combined with Hc+ candidates to form the Hb0 samples. Each Hb0 decay vertex is required to − be significantly displaced from all PVs in the event. For the Λ0b → Λ+ decay, the c π 0 reconstructed Λb trajectory must point back to one of the PVs in the event; only a very loose pointing requirement is imposed on the SL decay due to the momentum carried by the undetected particles. To reduce background in the SL decay samples, the z coordinates of the Hc+ and Hb0 decay vertices are required to satisfy z(Hc+ ) − z(Hb0 ) > −0.05 mm, where z is measured along the beam direction. Candidates that satisfy the invariant − 2 + − 2 mass requirements, 5.2 < M (Λ+ c π ) < 6.0 GeV/c or M (Hc µ ) < 8 GeV/c , are kept for further analysis. The symbol M designates the invariant mass of the system of indicated particle(s) throughout this Letter. To further suppress background in the Ξb0 → Ξc+ µ− X sample, a boosted decision tree (BDT) discriminant [37, 38] is used. The BDT exploits fourteen input variables, consisting of the χ2 values of the fitted Ξc+ and Ξb0 decay vertices, and the pT , p, χ2IP and a PID variable for each Ξc+ final-state particle. Simulated signal decays and background from the Ξc+ mass sidebands, 30 < |M (pK − π + ) − mΞc+ | < 60 MeV/c2 , in data are used to train the BDT, where the symbol m refers to the known mass of the indicated particle [39]. The PID response for final-state hadrons in the signal decay is obtained from large Λ → pπ − and D∗+ → (D0 → K − π + )π + calibration samples in data, which is weighted to reproduce the kinematics of the signal. The chosen requirement on the BDT response provides an efficiency of about 90% (40%) on the signal (background). − + − + 0 + − Figure 1 shows the mass spectra for Λ0b → Λ+ c π , Λc → pK π (from Λb → Λc µ X) − and Ξc+ → pK − π + (from Ξb0 → Ξc+ µ− X) candidates. For the Λ0b → Λ+ c π mode, a peak 0 + + at the known Λb mass is seen. For the SL modes, the Λc and Ξc mass peaks are used to determine the number of Λ0b and Ξb0 baryon decays, as the combinatorial background from random Hc+ µ− combinations is at the 1% level. The mass spectra are fit with the sum of two Gaussian functions with a common mean to represent the signal component and an exponential background function. The yields are given in Table 1. To form Ξb (6227)− candidates, a Λ0b (Ξb0 ) candidate is combined with a K − (π − ) 2

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− + 0 + − Figure 1: Invariant mass spectra for (top) Λ0b → Λ+ c π , (middle) Λc from Λb → Λc µ X, and + 0 + − (bottom) Ξc from Ξb → Ξc µ X candidate decays. The left column is for 7, 8 TeV and the − right is for 13 TeV data. Fits are overlaid, as described in the text. Here, the Λ0b → Λ+ c µ X mode has been prescaled by a factor of ten.

meson that has small χ2IP , consistent with being produced in the strong decay of the − 2 Ξb (6227)− resonance. Only Hb0 candidates satisfying |M (Λ+ c π )HAD − mΛ0b | < 60 MeV/c , |M (pK − π + )SL − mΛ+c | < 15 MeV/c2 , and |M (pK − π + )SL − mΞc+ | < 18 MeV/c2 are considered, where HAD and SL indicate the sample from which the mass is determined. We − π− require pK T > 800 MeV/c and pT > 900 MeV/c, based on an optimization of the expected statistical uncertainty on the Ξb (6227)− signal yield, using simulation to model the signal and either wrong-sign (Λ0b K + , Ξb0 π + ) or Ξb (6227)− mass sideband samples in data to 3

Table 1: Uncorrected Ξb (6227)− and Hb0 signal yields for 7, 8 and 13 TeV data. The Hb0 yields are limited to the signal regions used to form Ξb (6227)− candidates (see text).

Ξb (6227)− final state (Λ0b )HAD K − (Λ0b )SL K − (Ξb0 )SL π −

7, 8 TeV 13 TeV 3 − 0 N (Hb0 ) [103 ] N (Ξb (6227) ) N (Hb ) [10 ] N (Ξb (6227)− ) 170 ± 53 204.6 ± 0.5 215 ± 63 252.7 ± 0.6 2772 ± 325 3133 ± 6 3701 ± 432 3226 ± 6 351 ± 68 36.6 ± 0.3 274 ± 73 46.5 ± 0.3

model the background. After all selections the dominant source of background is due to combinations of real Λ0b (Ξb0 ) decays with a random K − (π − ) meson. All candidates satisfying these selections are retained. To improve the resolution on the Ξb (6227)− mass, we use the mass differences δmK ≡ M (Λ0b K − ) − M (Λ0b ) and δmπ ≡ M (Ξb0 π − ) − M (Ξb0 ), for the Λ0b K − and Ξb0 π − final states, respectively. The δmK(π) resolution is obtained from simulated Ξb (6227)− − decays, where the decay width is set to a negligible value. For the Λ0b → Λ+ c π mode, the 2 δmK resolution model is approximately Gaussian with a width of 2.4 MeV/c . For the SL decays, the missing momentum, pmiss , is estimated by assuming it is carried by a zero-mass particle that balances the momentum transverse to the Hb0 direction (formed from its decay vertex and PV), and satisfies the mass constraint (pHc+ + pµ− + pmiss )2 = m2H 0 . Mass b resolution shape parameters are obtained by fitting the δmK(π) spectra from simulated decays, which include contributions from excited charm baryons and final states with τ − leptons. The core of the resolution function has a half-width at half-maximum of about 20 MeV/c2 , and has a tail toward larger mass (see Appendix). The obtained shape parameters are fixed in the fits to data. The δmK and δmπ spectra in data are shown in Fig. 2. The Ξb (6227)− mass and width are obtained from a simultaneous unbinned maximum-likelihood fit to the δmK spectra − in 7, 8 and 13 TeV data, using the Λ0b → Λ+ c π mode. The signal shape is described by a P -wave relativistic Breit-Wigner function [40] with a Blatt-Weisskopf barrier factor [41], convoluted with a Gaussian resolution function of width 2.4 MeV/c2 . The mass and width are common parameters in the fit. The background shape is described by a smooth threshold function [42] with shape parameters that are freely and independently varied in the fits to the two data sets. A peak is observed in both data sets, with a mean δmpeak = 607.3 ± 2.0 MeV/c2 and width ΓΞb (6227)− = 18.1 ± 5.4 MeV/c2 . The peak has a K local statistical significance of about 7.9σ for the combined fit, based on the difference in log-likelihoods between a fit with zero signal and the best fit. The signal yields are given in Table 1. − The Ξb (6227)− → Λ0b K − decay with Λ0b → Λ+ c µ X is fit in a similar way, except for the different resolution function (see Appendix). A Gaussian constraint on the width of ΓΞb (6227)− = 18.1 ± 5.4 MeV/c2 is applied, as obtained from the fit to the hadronic mode, and the mean is freely varied. A peak is observed at a mass difference of 610.8 ± 1.0 (stat) MeV/c2 , which is consistent with that of the hadronic mode, and it contains a yield about 15 times larger, as expected. The statistical significance of this peak is about 25σ, thus clearly establishing this peaking structure. The Ξb0 π − final state is investigated by examining the δmπ spectra in 4

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Figure 2: Spectra of mass differences for Ξb (6227)− candidates, reconstructed in the final − 0 − 0 + − states (top) Λ0b K − , with Λ0b → Λ+ c π , (middle) Λb K , with Λb → Λc µ X, and (bottom) 0 − 0 + − Ξb π , with Ξb → Ξc µ X, along with the results of the fits. The left column is for 7, 8 TeV and the right is for 13 TeV data. The symbol M ∗ represents the mass after the constraint (pHc+ + pµ− + pmiss )2 = m2H 0 is applied, as described in the text. b

Ξb (6227)− → Ξb0 π − candidate decays, as shown in the bottom row of Fig. 2. The fit is performed in an analogous way to the δmK spectra, except for a different resolution function (see Appendix for δmπ resolution). The fitted mean of 440±5 MeV/c2 is consistent with the value expected from the hadronic mode of δmpeak + mΛ0b − mΞb0 = 435 ± 2 MeV/c2 . K The statistical significance of the peak is 9.2σ.

5

(0)

Table 2: Relative efficiencies (rel ) for the SL modes. Uncertainties are due only to the finite size of the simulated samples.

Final state Λ0b K − Ξb0 π −

7, 8 TeV 13 TeV 0.295 ± 0.006 0.305 ± 0.005 0.236 ± 0.007 0.277 ± 0.006

The production ratios are computed using N (Ξb (6227)− → Λ0b K − ) = κ, rel N (Λ0b ) N (Ξb (6227)− → Ξb0 π − ) 0 R(Ξb0 π − ) = κ , 0rel N (Ξb0 )

R(Λ0b K − )

(0)

(3) (4)

where N represents the yields in Table 1, and rel is the relative efficiency between the Ξb (6227)− and Hb0 selections, reported in Table 2. The quantity κ(0) represents corrections to the N (Hb0 ) SL signal yields to account for (i) random Hc+ µ− combinations, (ii) crossfeed from Ξb− → Ξc+ µ− X decays into the Ξb0 → Ξc+ µ− sample, and (iii) slightly different integrated luminosities used for the Ξb (6227)− and Hb0 samples. The contribution from random Hc+ µ− combinations is estimated from a study of the wrong-sign (Hc+ µ+ ) and right-sign (Hc+ µ− ) yields, from which a correction of 1.010 ± 0.002 to both R(Ξb0 π − ) and R(Λ0b K − ) is found. Cross-feeds from SL Ξb− decays, which must be subtracted from N (Ξb0 ), are inferred by adding a π − meson to the Ξc+ µ− candidate and searching for excited Ξc0 states. Mass peaks associated with the Ξc (2645)0 and Ξc (2790)0 resonances are observed, although for the former about half is due to Ξc (2815)+ → Ξc (2645)0 π + decays, as determined through a study of the Ξc+ π + mass spectrum. Since the Ξc (2815)+ µ− final state is predominantly from Ξb0 decays, this contribution is not subtracted. After correcting for the pion detection efficiency, we estimate that R(Ξb0 π − ) must be corrected by 1.11±0.03. Slightly different-size data samples are used for the Ξb (6227)− and inclusive Hb0 yield determinations, which amounts to corrections of less than 3%. A number of sources of systematic uncertainty have been considered. For the mass and width, the momentum scale uncertainty of 0.03% [43] leads to a 0.1 MeV/c2 uncertainty on δmK . A fit bias on the mass of 0.1 MeV/c2 is observed in simulation, and is corrected for and a systematic uncertainty of equal size is assigned. Uncertainty due to the signal shape model is estimated by using a nonrelativistic Breit-Wigner signal shape and varying the Gaussian resolution by ±10% about its nominal value. With these variations, systematic uncertainties of 0.2 MeV/c2 on δmK , and 0.9 MeV/c2 on ΓΞb (6227)− are obtained. Sensitivity to the background function is assessed by varying the fit range by 100 MeV/c2 on both ends, from which maximum shifts of 0.2 MeV/c2 in the mass and 1.6 MeV/c2 in the width are observed; these values are assigned as systematic uncertainties. Adding these systematic uncertainties in quadrature, leads to a total systematic uncertainty of 0.3 MeV/c2 on the mass and 1.8 MeV/c2 on the width. The systematic uncertainties affecting the production ratio measurements are listed in Table 3. The background shape affects the yield determination, and the associated systematic uncertainty is estimated by varying the fit range as described above. (Different 6

Table 3: Summary of systematic uncertainties on R(Λ0b K − ) and R(Ξb0 π − ), in units of 10−3 .

Source Background shape Signal shape Ξb (6227)− pT Tracking efficiency PID requirement N (Hb0 ) Simulated sample size Total

R(Λ0b K − ) [10−3 ] 7, 8 TeV 13 TeV 0.3 0.3 0.1 0.1

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background models give smaller deviations.) For the signal shape, the uncertainty is dominated by the resolution function. In an alternative fit, the resolution parameters are allowed to vary within twice the expected uncertainty and we take the difference with respect to the nominal result as the uncertainty. To assess the dependence on the kinematical properties of the Ξb (6227)− resonance, the pT spectrum in simulation is Ξ (6227)− weighted by 1 ± 0.01 × pTb /( GeV/c); the relative change in efficiency is assigned as a systematic uncertainty. The charged-particle tracking efficiency, obtained using (0) large samples of J/ψ → µ+ µ− decays [44], contributes an uncertainty of 1% to rel . The systematic uncertainty of the PID requirement on the K − or π − from the Ξb (6227)− baryon − + is determined by comparing the PID response of kaons and pions in the Λ+ c → pK π decay between data and simulation, where the latter are obtained from calibration data, as described previously. The uncertainty on N (Hb0 ) is taken as the quadratic sum of the uncertainties on the fitted yields and the uncertainties on the κ(0) corrections. Lastly, the finite size of the simulated samples is taken into account. In summary, we report the first observation of a new state, assumed to be an excited √ − Ξb state, using pp collision data samples collected by LHCb at s = 7 , 8 and 13 TeV. The mass and width are measured to be mΞb (6227)− − mΛ0b = 607.3 ± 2.0 (stat) ± 0.3 (syst) MeV/c2 , ΓΞb (6227)− = 18.1 ± 5.4 (stat) ± 1.8 (syst) MeV/c2 , mΞb (6227)− = 6226.9 ± 2.0 (stat) ± 0.3 (syst) ± 0.2(Λ0b ) MeV/c2 , where for the last result we have used mΛ0b = 5619.58 ± 0.17 MeV/c2 [39]. We have also measured the relative production rates to two final states, Λ0b K − and Ξb0 π − , as summarized in Table 4. The R(Λ0b K − ) values from the hadronic mode are consistent with those obtained in the SL mode, and are about an order of magnitude smaller than R(Ξb0 π − ). Assuming fΞb0 ' 0.1fΛ0b [45–47], we find that the ratio of branching fractions B(Ξb (6227)− → Λ0b K − )/B(Ξb (6227)− → Ξb0 π − ) ' 1, albeit with sizable uncertainty (≈ ±0.5) due to theoretical assumptions and the values of experimental inputs. The mass of this structure and the observed decay modes are consistent with expectations of either a Ξb (1P )− or Ξb (2S)− state [8–23]. As there are several excited 7

Table 4: Measured ratios R(Λ0b K − ) and R(Ξb0 π − ) for 7 , 8 and 13 TeV data, in units of 10−3 . The uncertainties are statistical (first) and systematic (second).

Quantity [10−3 ] 7 , 8 TeV 0 − R(Λb K ) 3.0 ± 0.3 ± 0.4 − R(Ξb π ) 47 ± 10 ± 7

13 TeV 3.4 ± 0.3 ± 0.4 22 ± 6 ± 3

Ξb− states expected in this mass region, the presence of more than one of these states contributing to this peak cannot be excluded. More precise measurements of the width and the relative branching fractions to Λ0b K − and Ξb0 π − , as well as Ξb 0 π − and Ξb ∗ π − , could help to determine the J P quantum numbers of this state [20].

Acknowledgements We express our gratitude to our colleagues in the CERN accelerator departments for the excellent performance of the LHC. We thank the technical and administrative staff at the LHCb institutes. We acknowledge support from CERN and from the national agencies: CAPES, CNPq, FAPERJ and FINEP (Brazil); MOST and NSFC (China); CNRS/IN2P3 (France); BMBF, DFG and MPG (Germany); INFN (Italy); NWO (The Netherlands); MNiSW and NCN (Poland); MEN/IFA (Romania); MinES and FASO (Russia); MinECo (Spain); SNSF and SER (Switzerland); NASU (Ukraine); STFC (United Kingdom); NSF (USA). We acknowledge the computing resources that are provided by CERN, IN2P3 (France), KIT and DESY (Germany), INFN (Italy), SURF (The Netherlands), PIC (Spain), GridPP (United Kingdom), RRCKI and Yandex LLC (Russia), CSCS (Switzerland), IFINHH (Romania), CBPF (Brazil), PL-GRID (Poland) and OSC (USA). We are indebted to the communities behind the multiple open-source software packages on which we depend. Individual groups or members have received support from AvH Foundation (Germany), EPLANET, Marie Sklodowska-Curie Actions and ERC (European Union), ANR, Labex P2IO and OCEVU, and R´egion Auvergne-Rhˆone-Alpes (France), Key Research Program of Frontier Sciences of CAS, CAS PIFI, and the Thousand Talents Program (China), RFBR, RSF and Yandex LLC (Russia), GVA, XuntaGal and GENCAT (Spain), Herchel Smith Fund, the Royal Society, the English-Speaking Union and the Leverhulme Trust (United Kingdom).

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Appendix

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Figure 3: Distribution of (left) M ∗ (Λ0b K − ) − M ∗ (Λ0b ) for simulated Ξb (6227)− → Λ0b K − decays, − ∗ 0 − ∗ 0 − → Ξ 0π− where Λ0b → Λ+ c µ X, and (right) M (Ξb π ) − M (Ξb ) for simulated Ξb (6227) b 0 + − ∗ decays, where Ξb → Ξc µ X. The symbol M represents the mass after the constraint (pHc+ + pµ− + pmiss )2 = m2H 0 is applied, as described in the text. The natural width used in the b simulation is set to a negligible value, so that these spectra are due entirely to the mass resolution. Fits to the sum of a nonrelativistic Breit-Wigner function and a Crystal Ball function [48] with a common mean value are overlaid.

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E. Graverini44 , G. Graziani17 , A. Grecu32 , R. Greim27 , P. Griffith22 , L. Grillo56 , L. Gruber42 , B.R. Gruberg Cazon57 , O. Gr¨ unberg67 , C. Gu3 , E. Gushchin36 , Yu. Guz39,42 , T. Gys42 , 62 57 C. G¨obel , T. Hadavizadeh , C. Hadjivasiliou5 , G. Haefeli43 , C. Haen42 , S.C. Haines49 , B. Hamilton60 , X. Han12 , T.H. Hancock57 , S. Hansmann-Menzemer12 , N. Harnew57 , S.T. Harnew48 , C. Hasse42 , M. Hatch42 , J. He63 , M. Hecker55 , K. Heinicke10 , A. Heister9 , K. Hennessy54 , L. Henry72 , E. van Herwijnen42 , M. Heß67 , A. Hicheur2 , D. Hill57 , M. Hilton56 , P.H. Hopchev43 , W. Hu65 , W. Huang63 , Z.C. Huard59 , W. Hulsbergen27 , T. Humair55 , M. Hushchyn37 , D. Hutchcroft54 , P. Ibis10 , M. Idzik30 , P. Ilten47 , K. Ivshin33 , R. Jacobsson42 , J. Jalocha57 , E. Jans27 , A. Jawahery60 , F. Jiang3 , M. John57 , D. Johnson42 , C.R. Jones49 , C. Joram42 , B. Jost42 , N. Jurik57 , S. Kandybei45 , M. Karacson42 , J.M. Kariuki48 , S. Karodia53 , N. Kazeev37 , M. Kecke12 , F. Keizer49 , M. Kelsey61 , M. Kenzie49 , T. Ketel28 , E. Khairullin37 , B. Khanji12 , C. Khurewathanakul43 , K.E. Kim61 , T. Kirn9 , S. Klaver18 , K. Klimaszewski31 , T. Klimkovich11 , S. Koliiev46 , M. Kolpin12 , R. Kopecna12 , P. Koppenburg27 , S. Kotriakhova33 , M. Kozeiha5 , L. Kravchuk36 , M. Kreps50 , F. Kress55 , P. Krokovny38,w , W. Krupa30 , W. Krzemien31 , W. Kucewicz29,l , M. Kucharczyk29 , V. Kudryavtsev38,w , A.K. Kuonen43 , T. Kvaratskheliya34,42 , D. Lacarrere42 , G. Lafferty56 , A. Lai22 , D. Lancierini44 , G. Lanfranchi18 , C. Langenbruch9 , T. Latham50 , C. Lazzeroni47 , R. Le Gac6 , A. Leflat35 , J. Lefran¸cois7 , R. Lef`evre5 , F. Lemaitre42 , O. Leroy6 , T. Lesiak29 , B. Leverington12 , P.-R. Li63 , T. Li3 , Z. Li61 , X. Liang61 , T. Likhomanenko69 , R. Lindner42 , F. Lionetto44 , V. Lisovskyi7 , X. Liu3 , D. Loh50 , A. Loi22 , I. Longstaff53 , J.H. Lopes2 , D. Lucchesi23,o , M. Lucio Martinez41 , A. Lupato23 , E. Luppi16,g , O. Lupton42 , A. Lusiani24 , X. Lyu63 , F. Machefert7 , F. Maciuc32 , V. Macko43 , P. Mackowiak10 , S. Maddrell-Mander48 , O. Maev33,42 , K. Maguire56 , D. Maisuzenko33 , M.W. Majewski30 , S. Malde57 , B. Malecki29 , A. Malinin69 , T. Maltsev38,w , G. Manca22,f , G. Mancinelli6 , D. Marangotto21,q , J. Maratas5,v , J.F. Marchand4 , U. Marconi15 , C. Marin Benito40 , M. Marinangeli43 , P. Marino43 , J. Marks12 , G. Martellotti26 , M. Martin6 , M. Martinelli43 , D. Martinez Santos41 , F. Martinez Vidal72 , A. Massafferri1 , R. Matev42 , A. Mathad50 , Z. Mathe42 , C. Matteuzzi20 , A. Mauri44 , E. Maurice7,b , B. Maurin43 , A. Mazurov47 , M. McCann55,42 , A. McNab56 , R. McNulty13 , J.V. Mead54 , B. Meadows59 , C. Meaux6 , F. Meier10 , N. Meinert67 , D. Melnychuk31 , M. Merk27 , A. Merli21,q , E. Michielin23 , D.A. Milanes66 , E. Millard50 , M.-N. Minard4 , L. Minzoni16,g , D.S. Mitzel12 , A. Mogini8 , J. Molina Rodriguez1,z , T. Momb¨ acher10 , I.A. Monroy66 , S. Monteil5 , M. Morandin23 , G. Morello18 , M.J. Morello24,t , O. Morgunova69 , J. Moron30 , A.B. Morris6 , R. Mountain61 , F. Muheim52 , M. Mulder27 , D. M¨ uller42 , J. M¨ uller10 , K. M¨ uller44 , V. M¨ uller10 , P. Naik48 , 43 51 57 43 2 T. Nakada , R. Nandakumar , A. Nandi , T. Nanut , I. Nasteva , M. Needham52 , N. Neri21 , S. Neubert12 , N. Neufeld42 , M. Neuner12 , T.D. Nguyen43 , C. Nguyen-Mau43,n , S. Nieswand9 , R. Niet10 , N. Nikitin35 , A. Nogay69 , D.P. O’Hanlon15 , A. Oblakowska-Mucha30 , V. Obraztsov39 , S. Ogilvy18 , R. Oldeman22,f , C.J.G. Onderwater68 , A. Ossowska29 , J.M. Otalora Goicochea2 , P. Owen44 , A. Oyanguren72 , P.R. Pais43 , A. Palano14 , M. Palutan18,42 , G. Panshin71 , A. Papanestis51 , M. Pappagallo52 , L.L. Pappalardo16,g , W. Parker60 , C. Parkes56 , G. Passaleva17,42 , A. Pastore14 , M. Patel55 , C. Patrignani15,e , A. Pearce42 , A. Pellegrino27 , G. Penso26 , M. Pepe Altarelli42 , S. Perazzini42 , D. Pereima34 , P. Perret5 , L. Pescatore43 , K. Petridis48 , A. Petrolini19,h , A. Petrov69 , M. Petruzzo21,q , B. Pietrzyk4 , G. Pietrzyk43 , M. Pikies29 , D. Pinci26 , J. Pinzino42 , F. Pisani42 , A. Pistone19,h , A. Piucci12 , V. Placinta32 , S. Playfer52 , J. Plews47 , M. Plo Casasus41 , F. Polci8 , M. Poli Lener18 , A. Poluektov50 , N. Polukhina70,c , I. Polyakov61 , E. Polycarpo2 , G.J. Pomery48 , S. Ponce42 , A. Popov39 , D. Popov47,11 , S. Poslavskii39 , C. Potterat2 , E. Price48 , J. Prisciandaro41 , C. Prouve48 , V. Pugatch46 , A. Puig Navarro44 , H. Pullen57 , G. Punzi24,p , W. Qian63 , J. Qin63 , R. Quagliani8 , B. Quintana5 , B. Rachwal30 , J.H. Rademacker48 , M. Rama24 , M. Ramos Pernas41 , M.S. Rangel2 , F. Ratnikov37,x , G. Raven28 , M. Ravonel Salzgeber42 , M. Reboud4 , F. Redi43 , S. Reichert10 , A.C. dos Reis1 , F. Reiss8 , C. Remon Alepuz72 , Z. Ren3 , V. Renaudin7 ,

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S. Ricciardi51 , S. Richards48 , K. Rinnert54 , P. Robbe7 , A. Robert8 , A.B. Rodrigues43 , E. Rodrigues59 , J.A. Rodriguez Lopez66 , A. Rogozhnikov37 , S. Roiser42 , A. Rollings57 , V. Romanovskiy39 , A. Romero Vidal41 , M. Rotondo18 , M.S. Rudolph61 , T. Ruf42 , J. Ruiz Vidal72 , J.J. Saborido Silva41 , N. Sagidova33 , B. Saitta22,f , V. Salustino Guimaraes62 , C. Sanchez Gras27 , C. Sanchez Mayordomo72 , B. Sanmartin Sedes41 , R. Santacesaria26 , C. Santamarina Rios41 , M. Santimaria18 , E. Santovetti25,j , G. Sarpis56 , A. Sarti18,k , C. Satriano26,s , A. Satta25 , M. Saur63 , D. Savrina34,35 , S. Schael9 , M. Schellenberg10 , M. Schiller53 , H. Schindler42 , M. Schmelling11 , T. Schmelzer10 , B. Schmidt42 , O. Schneider43 , A. Schopper42 , H.F. Schreiner59 , M. Schubiger43 , M.H. Schune7 , R. Schwemmer42 , B. Sciascia18 , A. Sciubba26,k , A. Semennikov34 , E.S. Sepulveda8 , A. Sergi47,42 , N. Serra44 , J. Serrano6 , L. Sestini23 , P. Seyfert42 , M. Shapkin39 , Y. Shcheglov33,† , T. Shears54 , L. Shekhtman38,w , V. Shevchenko69 , E. Shmanin70 , B.G. Siddi16 , R. Silva Coutinho44 , L. Silva de Oliveira2 , G. Simi23,o , S. Simone14,d , N. Skidmore12 , T. Skwarnicki61 , E. Smith9 , I.T. Smith52 , M. Smith55 , M. Soares15 , l. Soares Lavra1 , M.D. Sokoloff59 , F.J.P. Soler53 , B. Souza De Paula2 , B. Spaan10 , P. Spradlin53 , F. Stagni42 , M. Stahl12 , S. Stahl42 , P. Stefko43 , S. Stefkova55 , O. Steinkamp44 , S. Stemmle12 , O. Stenyakin39 , M. Stepanova33 , H. Stevens10 , S. Stone61 , B. Storaci44 , S. Stracka24,p , M.E. Stramaglia43 , M. Straticiuc32 , U. Straumann44 , S. Strokov71 , J. Sun3 , L. Sun64 , K. Swientek30 , V. Syropoulos28 , T. Szumlak30 , M. Szymanski63 , S. T’Jampens4 , Z. Tang3 , A. Tayduganov6 , T. Tekampe10 , G. Tellarini16 , F. Teubert42 , E. Thomas42 , J. van Tilburg27 , M.J. Tilley55 , V. Tisserand5 , M. Tobin43 , S. Tolk42 , L. Tomassetti16,g , D. Tonelli24 , D.Y. Tou8 , R. Tourinho Jadallah Aoude1 , E. Tournefier4 , M. Traill53 , M.T. Tran43 , A. Trisovic49 , A. Tsaregorodtsev6 , A. Tully49 , N. Tuning27,42 , A. Ukleja31 , A. Usachov7 , A. Ustyuzhanin37 , U. Uwer12 , C. Vacca22,f , A. Vagner71 , V. Vagnoni15 , A. Valassi42 , S. Valat42 , G. Valenti15 , R. Vazquez Gomez42 , P. Vazquez Regueiro41 , S. Vecchi16 , M. van Veghel27 , J.J. Velthuis48 , M. Veltri17,r , G. Veneziano57 , A. Venkateswaran61 , T.A. Verlage9 , M. Vernet5 , M. Vesterinen57 , J.V. Viana Barbosa42 , D. Vieira63 , M. Vieites Diaz41 , H. Viemann67 , X. Vilasis-Cardona40,m , A. Vitkovskiy27 , M. Vitti49 , V. Volkov35 , A. Vollhardt44 , B. Voneki42 , A. Vorobyev33 , V. Vorobyev38,w , C. Voß9 , J.A. de Vries27 , C. V´azquez Sierra27 , R. Waldi67 , J. Walsh24 , J. Wang61 , M. Wang3 , Y. Wang65 , Z. Wang44 , D.R. Ward49 , H.M. Wark54 , N.K. Watson47 , D. Websdale55 , A. Weiden44 , C. Weisser58 , M. Whitehead9 , J. Wicht50 , G. Wilkinson57 , M. Wilkinson61 , M.R.J. Williams56 , M. Williams58 , T. Williams47 , F.F. Wilson51,42 , J. Wimberley60 , M. Winn7 , J. Wishahi10 , W. Wislicki31 , M. Witek29 , G. Wormser7 , S.A. Wotton49 , K. Wyllie42 , D. Xiao65 , Y. Xie65 , A. Xu3 , M. Xu65 , Q. Xu63 , Z. Xu3 , Z. Xu4 , Z. Yang3 , Z. Yang60 , Y. Yao61 , H. Yin65 , J. Yu65,ab , X. Yuan61 , O. Yushchenko39 , K.A. Zarebski47 , M. Zavertyaev11,c , D. Zhang65 , L. Zhang3 , W.C. Zhang3,aa , Y. Zhang7 , A. Zhelezov12 , Y. Zheng63 , X. Zhu3 , V. Zhukov9,35 , J.B. Zonneveld52 , S. Zucchelli15 . 1

Centro Brasileiro de Pesquisas F´ısicas (CBPF), Rio de Janeiro, Brazil Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, Brazil 3 Center for High Energy Physics, Tsinghua University, Beijing, China 4 Univ. Grenoble Alpes, Univ. Savoie Mont Blanc, CNRS, IN2P3-LAPP, Annecy, France 5 Clermont Universit´e, Universit´e Blaise Pascal, CNRS/IN2P3, LPC, Clermont-Ferrand, France 6 Aix Marseille Univ, CNRS/IN2P3, CPPM, Marseille, France 7 LAL, Univ. Paris-Sud, CNRS/IN2P3, Universit´e Paris-Saclay, Orsay, France 8 LPNHE, Universit´e Pierre et Marie Curie, Universit´e Paris Diderot, CNRS/IN2P3, Paris, France 9 I. Physikalisches Institut, RWTH Aachen University, Aachen, Germany 10 Fakult¨ at Physik, Technische Universit¨ at Dortmund, Dortmund, Germany 11 Max-Planck-Institut f¨ ur Kernphysik (MPIK), Heidelberg, Germany 12 Physikalisches Institut, Ruprecht-Karls-Universit¨ at Heidelberg, Heidelberg, Germany 13 School of Physics, University College Dublin, Dublin, Ireland 14 INFN Sezione di Bari, Bari, Italy 15 INFN Sezione di Bologna, Bologna, Italy 2

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INFN Sezione di Ferrara, Ferrara, Italy INFN Sezione di Firenze, Firenze, Italy 18 INFN Laboratori Nazionali di Frascati, Frascati, Italy 19 INFN Sezione di Genova, Genova, Italy 20 INFN Sezione di Milano-Bicocca, Milano, Italy 21 INFN Sezione di Milano, Milano, Italy 22 INFN Sezione di Cagliari, Monserrato, Italy 23 INFN Sezione di Padova, Padova, Italy 24 INFN Sezione di Pisa, Pisa, Italy 25 INFN Sezione di Roma Tor Vergata, Roma, Italy 26 INFN Sezione di Roma La Sapienza, Roma, Italy 27 Nikhef National Institute for Subatomic Physics, Amsterdam, Netherlands 28 Nikhef National Institute for Subatomic Physics and VU University Amsterdam, Amsterdam, Netherlands 29 Henryk Niewodniczanski Institute of Nuclear Physics Polish Academy of Sciences, Krak´ ow, Poland 30 AGH - University of Science and Technology, Faculty of Physics and Applied Computer Science, Krak´ ow, Poland 31 National Center for Nuclear Research (NCBJ), Warsaw, Poland 32 Horia Hulubei National Institute of Physics and Nuclear Engineering, Bucharest-Magurele, Romania 33 Petersburg Nuclear Physics Institute (PNPI), Gatchina, Russia 34 Institute of Theoretical and Experimental Physics (ITEP), Moscow, Russia 35 Institute of Nuclear Physics, Moscow State University (SINP MSU), Moscow, Russia 36 Institute for Nuclear Research of the Russian Academy of Sciences (INR RAS), Moscow, Russia 37 Yandex School of Data Analysis, Moscow, Russia 38 Budker Institute of Nuclear Physics (SB RAS), Novosibirsk, Russia 39 Institute for High Energy Physics (IHEP), Protvino, Russia 40 ICCUB, Universitat de Barcelona, Barcelona, Spain 41 Instituto Galego de F´ısica de Altas Enerx´ıas (IGFAE), Universidade de Santiago de Compostela, Santiago de Compostela, Spain 42 European Organization for Nuclear Research (CERN), Geneva, Switzerland 43 Institute of Physics, Ecole Polytechnique F´ed´erale de Lausanne (EPFL), Lausanne, Switzerland 44 Physik-Institut, Universit¨ at Z¨ urich, Z¨ urich, Switzerland 45 NSC Kharkiv Institute of Physics and Technology (NSC KIPT), Kharkiv, Ukraine 46 Institute for Nuclear Research of the National Academy of Sciences (KINR), Kyiv, Ukraine 47 University of Birmingham, Birmingham, United Kingdom 48 H.H. Wills Physics Laboratory, University of Bristol, Bristol, United Kingdom 49 Cavendish Laboratory, University of Cambridge, Cambridge, United Kingdom 50 Department of Physics, University of Warwick, Coventry, United Kingdom 51 STFC Rutherford Appleton Laboratory, Didcot, United Kingdom 52 School of Physics and Astronomy, University of Edinburgh, Edinburgh, United Kingdom 53 School of Physics and Astronomy, University of Glasgow, Glasgow, United Kingdom 54 Oliver Lodge Laboratory, University of Liverpool, Liverpool, United Kingdom 55 Imperial College London, London, United Kingdom 56 School of Physics and Astronomy, University of Manchester, Manchester, United Kingdom 57 Department of Physics, University of Oxford, Oxford, United Kingdom 58 Massachusetts Institute of Technology, Cambridge, MA, United States 59 University of Cincinnati, Cincinnati, OH, United States 60 University of Maryland, College Park, MD, United States 61 Syracuse University, Syracuse, NY, United States 62 Pontif´ıcia Universidade Cat´ olica do Rio de Janeiro (PUC-Rio), Rio de Janeiro, Brazil, associated to 2 63 University of Chinese Academy of Sciences, Beijing, China, associated to 3 64 School of Physics and Technology, Wuhan University, Wuhan, China, associated to 3 65 Institute of Particle Physics, Central China Normal University, Wuhan, Hubei, China, associated to 3 66 Departamento de Fisica , Universidad Nacional de Colombia, Bogota, Colombia, associated to 8 67 Institut f¨ ur Physik, Universit¨ at Rostock, Rostock, Germany, associated to 12 68 Van Swinderen Institute, University of Groningen, Groningen, Netherlands, associated to 27 17

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National Research Centre Kurchatov Institute, Moscow, Russia, associated to 34 National University of Science and Technology ”MISIS”, Moscow, Russia, associated to 34 71 National Research Tomsk Polytechnic University, Tomsk, Russia, associated to 34 72 Instituto de Fisica Corpuscular, Centro Mixto Universidad de Valencia - CSIC, Valencia, Spain, associated to 40 73 University of Michigan, Ann Arbor, United States, associated to 61 74 Los Alamos National Laboratory (LANL), Los Alamos, United States, associated to 61 70

a

Universidade Federal do Triˆ angulo Mineiro (UFTM), Uberaba-MG, Brazil Laboratoire Leprince-Ringuet, Palaiseau, France c P.N. Lebedev Physical Institute, Russian Academy of Science (LPI RAS), Moscow, Russia d Universit` a di Bari, Bari, Italy e Universit` a di Bologna, Bologna, Italy f Universit` a di Cagliari, Cagliari, Italy g Universit` a di Ferrara, Ferrara, Italy h Universit` a di Genova, Genova, Italy i Universit` a di Milano Bicocca, Milano, Italy j Universit` a di Roma Tor Vergata, Roma, Italy k Universit` a di Roma La Sapienza, Roma, Italy l AGH - University of Science and Technology, Faculty of Computer Science, Electronics and Telecommunications, Krak´ ow, Poland m LIFAELS, La Salle, Universitat Ramon Llull, Barcelona, Spain n Hanoi University of Science, Hanoi, Vietnam o Universit` a di Padova, Padova, Italy p Universit` a di Pisa, Pisa, Italy q Universit` a degli Studi di Milano, Milano, Italy r Universit` a di Urbino, Urbino, Italy s Universit` a della Basilicata, Potenza, Italy t Scuola Normale Superiore, Pisa, Italy u Universit` a di Modena e Reggio Emilia, Modena, Italy v MSU - Iligan Institute of Technology (MSU-IIT), Iligan, Philippines w Novosibirsk State University, Novosibirsk, Russia x National Research University Higher School of Economics, Moscow, Russia y Sezione INFN di Trieste, Trieste, Italy z Escuela Agr´ıcola Panamericana, San Antonio de Oriente, Honduras aa School of Physics and Information Technology, Shaanxi Normal University (SNNU), Xi’an, China ab Physics and Micro Electronic College, Hunan University, Changsha City, China b



Deceased

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